Respiratory physiology & neurobiology
-
Respir Physiol Neurobiol · Aug 2010
Randomized Controlled Trial Clinical TrialReversibility of inspiratory lung function parameters after short-term bronchodilators in COPD.
The responsiveness of short-term bronchodilator use on inspiratory lung function parameters (ILPs), including Forced Inspiratory Volume in one second (FIV(1)), Inspiratory Capacity (IC), Forced Inspiratory Flow at 50% of the vital capacity (FIF(50)), Peak Inspiratory Flow (PIF) and on the relationship between these values and dyspnea in COPD subjects has been examined only sparsely in past studies. The aim of this study was to assess the effects of inhaled salbutamol 400 mcg, ipratropium 80 mcg and a placebo on ILP and FEV(1) and their relationship to dyspnea, as measured with a Visual Analogue Scale (VAS). ⋯ In subjects with COPD, all ILP, FEV(1) values and VAS scores showed significant improvements after bronchodilator use as well as with placebo. However, ILPs were not more sensitive than FEV(1) for detecting responders after bronchodilator use or changes in the VAS score.
-
Time-dependent characteristics of the flow in a human nasal airway constructed from the CT image of a healthy volunteer were investigated using a computational fluid dynamics (CFD) technique. To capture the time-varying nature of the flow as well as pressure and temperature fields, the large eddy simulation (LES) technique instead of the RANS (Reynolds Averaged Navier-Stokes) approach was adopted. To make the present analysis more relevant to a real human breathing cycle, the flow was designed to be induced by the pressure difference and the time-varying pressure at the end of trachea was described to reproduce the flow rate data from the measurement. ⋯ Also, the fact that the distribution of the flow rate in a given cross-section of the airway changes significantly with time implies the importance of unsteady data for clinical decision. The wall shear stress was found to have relatively high values at the locations near nasopharynx and larynx but the magnitude changes with time during the whole respiratory cycle. Analysis of the temperature field showed that most of the temperature change occurs in the nasal cavity when the air is incoming and thus, the nasal cavity acts as a very efficient heat exchanger during an inspiration period.
-
Respir Physiol Neurobiol · Jul 2010
Methylxanthine reversal of opioid-evoked inspiratory depression via phosphodiesterase-4 blockade.
Hypothetic mechanisms for respirogenic methylxanthine actions include blockade of adenosine receptors or phosphodiesterase-4 (PDE4) in inspiratory pre-Bötzinger complex (preBötC) networks. Here, we studied this by analyzing stimulating caffeine and theophylline actions on mu-opioid-depressed inspiratory-related rhythm in the ventrolateral aspect of rat brainstem slices. The methylxanthines restored DAMGO (0.5-1 microM) depressed rhythm only at >1mM, which is approximately 10-fold higher than selective for adenosine receptors. ⋯ At 0.25 microM, rolipram boosted incomplete recovery by 1 mM theophylline of DAMGO-depressed rhythm. Findings indicate that methylxanthines excite rhythmogenic preBötC networks via blockade of cAMP dependent PDE4 and suggest that specific PDE4 inhibitors (plus low methylxanthine doses) stimulate breathing effectively. We discuss why methylxanthine doses for preBötC stimulation need to be higher than those for respirogenic effects in vivo.
-
Respir Physiol Neurobiol · Jul 2010
Effects of gender and posture on thoraco-abdominal kinematics during quiet breathing in healthy adults.
To investigate the effects of posture and gender on thoraco-abdominal motion and breathing pattern, 34 healthy men and women were studied by Opto-Electronic Plethysmography during quiet breathing in five different postures from seated (with and without back support) to supine position. Chest wall kinematics and breathing pattern were significantly influenced by position and gender. The progressively increased inclination of the trunk determined a progressive reduction of rib cage displacement, tidal volume, and minute ventilation and a progressive increase of abdominal contribution to tidal volume. ⋯ The effect of posture on abdominal kinematics was significant only in women. The presence of a back support in seated position determined differences in breathing pattern. In conclusion, posture and gender have a strong influence on breathing and on chest wall kinematics.
-
Respir Physiol Neurobiol · Jun 2010
Significance of hemoglobin concentration in determining blood CO2 binding capacity in critical illness.
This study was performed to provide simplified quantitative evidence of the impact of hemoglobin concentration on blood CO(2) binding and transport capacity. Linear regression equations were obtained for gas analyses data obtained from 85 surgical patients with sepsis and various degrees of illness. Venoarterial CO(2) concentration differences were calculated by a complex procedure, and then simplified equations were derived to highlight the impact of hemoglobin concentration on blood CO(2) binding and the Haldane effect. The results showed that, although in normal conditions the impact of hemoglobin concentration is less evident, it becomes relevant in extreme conditions, also protecting against venous and tissue hypercapnia and acidosis.